This invention pertains to the art of vehicle brakes, and more specifically to an arrangement which is used to indicate excessive brake lining wear.
Various brake wear indicators are known in the prior art as represented as U.S. Pat. Nos. 3,533,491, 3,983,964, 4,136,634, 4,186,822 and 4,356,897. These known brake wear indicators depend upon visually sensing the amount of brake wear. These systems are cumbersome in that many times the vehicle wheel must be first removed before the brake wear can be determined and often times it is difficult, either due to lighting problems or obstructions, to view these indicators. Also known in the art are brake wear indicators which depend on sound. In these systems, when the brake lining is worn beyond a permissible amount, an audible sound is produced. Most of these systems however require a noise producing element to be imbedded in the brake lining which increases the costs and presents difficulties in manufacturing these liners.
It is extremely difficult, especially in heavy-duty work vehicles, to remove the wheels in order to view the "sight" type indicators and due to the more frequent replacement of brake linings in such vehicles, the additional cost of imbedding a sound producing element in the brake lining itself is not desirable.
The brake systems in many heavy duty work vehicles include various friction plates which rotate in unison with a vehicle wheel, various brake discs which are interposed between the friction plates and which are fixed against rotation relative to the wheel, and a piston, which when activated, engages the brake disc and the friction plates in order to brake the vehicle. This entire system is often located within a housing and therefore would require the disassembling of the housing in order to view the amount of brake wear.
One of the major drawbacks of the prior art brake wear indicator systems is the fact that these systems are not readily accessible to the operator. This is due mainly to the fact that the indicator extends in the direction of movement of the brake discs and piston. The brake disc lining wear indicator disclosed in French Patent Publication No. 2,404,150, issued May 25, 1979, is more readily accessible since the indicator extends perpendicular to the direction of movement of the brake discs and piston. However, due to the location of the indicator, the French system fails to sense the total accumulative wear on the entire brake system. Furthermore, the indicator is located at the frictional surfaces making it susceptible to contamination from the wearing brake linings.
Therefore there is a need for a brake lining wear indicator system which will provide a quick method of checking brake wear without the need to remove the wheels or to imbed special elements in the brake liners, will be easily accessible, will sense the total cumulative wear of the brake system, and which will be located in any area remote from the debris associated with the wearing of the brake linings.